I like the fact we have a standardised UI across the whole platform.

There was nothing worse on previous versions than having basically each app implementing its own UI standards. Having the same menus, the same content disposition makes it easier for users to pre-empt and understand where the options are, and how they can achieve or look for things. This, in my opinion, is the greatest advancement in the platform.

I also like the integration in the UI itself of all the communication services (Flickr, IM clients, Skype). It gives a very rugged and completeness feel to the platform as a whole.